U.S. Pat. No. 4,364,764 (Farkas et al.), the disclosure of which is incorporated by reference herein, in FIG. 1, illustrates a series of steps that are followed in producing hollow glass containers from gobs of glass at a formable temperature on a glass container forming machine of the I.S. type by a process known as the blow and blow process. In the blow and blow process as practiced on an I.S. machine, a preform of a glass container is formed in an inverted orientation, that is, with its open end down, in a first stage mold, which is often called a blank mold. The preform, which is often called a blank or a parison, is then transferred by an inverting operation through an arc of 180° into a second stage mold, which is often called a blow mold, where the preform is blown into its final configuration. View C of FIG. 2 of the '764 patent illustrates a step in the blow and blow process that is described as the counterblow step, a step in which blowing air is injected into a parison after the parison is properly settled at the bottom of the blank mold.
U.S. Pat. No. 4,191,548 (Fortner et al.), the disclosure of which is also incorporated by reference herein, discloses specific apparatus for introducing counterblow air into a glass preform in a blank mold of a I.S. machine that is operated on the blow and blow process.
Heretofore, counterblow air for use in the blow and blow process as practiced on an I.S. machine has been introduced into a gob of glass in the I.S. forming machine blank mold through a plunger that reciprocates with respect to the mold, and the glass gob therein that is to be blown into the desired shape of a parison, the counterblow air being blown only when the plunger is in its down position. This step is taught, for example, by the aforesaid Fortner et al. '548 patent at column 5, lines 49–57. The step of withdrawing the plunger during introduction of counterblow air can, however, lead to the distortion of the “corkage” of the finish portion of the parison, as the term “corkage” is used in the aforesaid '548 patent.